Embodiments of the present invention generally relate to methods for depositing pure metal. Specific embodiments of the invention are directed to methods for pure metal deposition using CVD or ALD techniques.
Hydrogen plasma is often utilized to enable pure metal deposition by using CVD or ALD techniques. Typically, a metal precursor is used as a metal source. As schematically shown in FIG. 1, hydrogen plasma is utilized to reduce the precursor or to treat a deposited film to improve film properties, such as purity, resistivity and/or grain structure and is deposited typically on a gate dielectric layer 110, typically comprising HfO, SiON and/or SiO2, disposed on an active area or underlying Si layer 120.
Damage to the underlying layers is a concern in processes that include, but are not limited to, metal gate deposition, formation of a treatment film on a low K films, and silicide deposition. In metal gate deposition, the substrate may be Si and may include a thin oxide layer deposited on the Si substrate having a thickness of less than about 10 , a high K oxide disposed on the thin oxide layer having a thickness less than about 20 , an optional cap layer having a thickness in the range from about 10  to about 20  and a metal gate layer such as a tantalum or cobalt metal layer. In processes for providing a treatment film on a low K film, the substrate includes a low K material, a barrier layer deposited on the substrate followed by a metal deposition on the barrier layer or treatment of the barrier layer. The barrier layer in such processes is typically thin. In silicide deposition, the substrate typically includes Si and includes a metal silicide layer disposed thereon and cleaned and a barrier layer is disposed on the metal silicide layer.
There is a need to provide methods that utilize the benefits of hydrogen plasma in pure metal deposition but control or eliminate the damage that hydrogen plasma can cause.